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Periodic Classification of Elements PYQs – Chemistry, SSC & Railway

56 Periodic Classification of Elements (Chemistry) questions asked in recent SSC and Railway exams, newest first, with exam, date & shift, answers and solutions.

📚 56 questionsSSC 5 · Railway 51
RRB Group D 2025-26 – 25 August 2026 Shift 2 · Element facts (names, symbols, atomic numbers)

Q1. Which of the following is the correct symbol for the element Aluminium?

  1. (a) Alm
  2. (b) alm
  3. (c) AL
  4. (d) Al
Answer & solution

Answer: (d) Al

Correct Answer:
Correct Answer: Option 4 – Al
Explanation:
The correct chemical symbol for the elementAluminiumis'Al'— with the first letter capitalized and the second letter in lowercase, following standard IUPAC convention for element symbols derived from a name (first letter uppercase, subsequent letter(s) lowercase). 'Alm', 'alm', and 'AL' are not valid element symbol formats.
RRB Group D 2025-26 – 20 August 2026 Shift 2 · Element facts (names, symbols, atomic numbers)

Q2. Which of the following elements has a mass number of 40 and atomic number of 20?

  1. (a) Calcium
  2. (b) Neon
  3. (c) Sodium
  4. (d) Potassium
Answer & solution

Answer: (a) Calcium

Correct Answer:
Correct Answer: Option 1 – Calcium
Explanation:
Calcium (Ca) has atomic number 20 (20 protons) and its most common isotope has mass number 40 (20 protons + 20 neutrons).
Important Facts:
• Neon: atomic number 10.
• Sodium: atomic number 11.
• Potassium: atomic number 19, mass number 39.
RRB Group D 2025-26 – 14 August 2026 Shift 1 · Element facts (names, symbols, atomic numbers)

Q3. Which of the following pairs is correctly matched?

  1. (a) Fe – Fluorine
  2. (b) Ag – Argon
  3. (c) Au – Aluminum
  4. (d) Pb – Lead
Answer & solution

Answer: (d) Pb – Lead

Answer: Option 4 – Pb – Lead.
•Pbis the symbol forLead(Latin *plumbum*). The others are mismatched.
RRB Group D 2025-26 – 13 August 2026 Shift 2 · Element facts (names, symbols, atomic numbers)

Q4. The element with the symbol K is:

  1. (a) Phosphorous
  2. (b) Palladium
  3. (c) Potassium
  4. (d) Krypton
Answer & solution

Answer: (c) Potassium

Answer: Option 3 – Potassium.
• The symbolKstands forPotassium(from Latin *kalium*).
RRB Group D 2025-26 – 12 August 2026 Shift 2 · Element facts (names, symbols, atomic numbers)

Q5. Which rule for writing chemical symbols is correct?

  1. (a) First letter capital only
  2. (b) Both letters capitalised
  3. (c) Letters written in italics
  4. (d) Second letter capital only
Answer & solution

Answer: (a) First letter capital only

Answer: Option 1 – First letter capital only.
• A chemical symbol has thefirst letter capital and the second (if any) small(e.g. Na, Cl).
RRB Group D 2025-26 – 6 August 2026 Shift 3 · Element facts (names, symbols, atomic numbers)

Q6. Which of the following element symbols does NOT match its element?

  1. (a) C for Carbon
  2. (b) Sb for Seaborgium
  3. (c) O for Oxygen
  4. (d) As for Arsenic
Answer & solution

Answer: (b) Sb for Seaborgium

Answer: Option 2 — Sb for Seaborgium
Sbis the symbol forAntimony, not Seaborgium (Sg). So this pairing is wrong → Option 2.
RRB Group D 2025-26 – 5 August 2026 Shift 3 · Periodic trends (atomic size, metallic character, electronegativity, ionisation energy)

Q7. Which statement best identifies a metalloid based on its properties?

  1. (a) It shows properties that are unrelated to metals and non-metals
  2. (b) It shows properties identical to non-metals in all conditions
  3. (c) It shows properties intermediate between metals and non-metals
  4. (d) It shows properties identical to metals in all conditions
Answer & solution

Answer: (c) It shows properties intermediate between metals and non-metals

Answer: Option 3 — Intermediate between metals and non-metals
Ametalloid(e.g., silicon, boron) shows propertiesin betweenthose of metals and non-metals → Option 3.
RRB Group D 2025-26 – 5 August 2026 Shift 3 · Element facts (names, symbols, atomic numbers)

Q8. Which of the following statement(s) is/are true?Statement I: The symbol 'Ag' stands for gold.Statement II: The symbol 'Pb' represents lead.

  1. (a) Both statements are incorrect
  2. (b) Both statements are correct
  3. (c) Statement I is incorrect, Statement II is correct
  4. (d) Statement I is correct, Statement II is incorrect
Answer & solution

Answer: (c) Statement I is incorrect, Statement II is correct

Answer: Option 3 — Statement I incorrect, Statement II correct
'Ag' issilver(not gold) — I is wrong. 'Pb' islead— II is correct → Option 3.
RRB NTPC UG CBT-1 2025-26 – 20 June 2026 Shift 2 · Element families (alkali, alkaline earth, halogens, noble gases)

Q9. Considering the periodic trends, which property explains why noble gases are chemically inert under standard conditions?

  1. (a) Low ionization energy
  2. (b) High atomic mass
  3. (c) High electronegativity
  4. (d) Completely filled valence shell
Answer & solution

Answer: (d) Completely filled valence shell

Topic: Noble Gases - Chemical Inertness
Noble gases havecompletely filled valence shells(ns²np⁶ configuration).
This stable electronic configuration makes them highly unreactive as they have no tendency to gain, lose, or share electrons.
Examples: He (1s²), Ne (2s²2p⁶), Ar (3s²3p⁶)
Other options incorrect:
• Noble gases havehigh ionization energy(not low)
• Atomic mass doesn't determine reactivity
• Electronegativity is negligible for noble gases
Answer: Option 4 → Completely filled valence shell
RRB NTPC UG CBT-1 2025-26 – 19 June 2026 Shift 2 · Groups and periods - position of elements

Q10. In the context of periodicity, elements in the same group tend to display similar chemical properties. Which primary factor is responsible for this similarity among group members?

  1. (a) Similar valence electronic configuration
  2. (b) Similar atomic masses
  3. (c) Constant atomic radius
  4. (d) Identical atomic numbers
Answer & solution

Answer: (a) Similar valence electronic configuration

Topic: Periodic Table - Group Properties
Elements in the same group havesame number of valence electrons.
Key Facts:
• Valence electrons determine chemical reactivity and bonding behavior
• Group 1: All have 1 valence electron (Li, Na, K)
• Group 17: All have 7 valence electrons (F, Cl, Br)
Atomic mass, radius, and atomic number vary within a group.
Onlyvalence electronic configuration remains similar.
Answer: Option 1 → Similar valence electronic configuration
RRB NTPC UG CBT-1 2025-26 – 18 June 2026 Shift 2 · Groups and periods - position of elements

Q11. When moving down a group in the Modern Periodic Table, what happens to the number of valence electrons?

  1. (a) Increases by one
  2. (b) Decreases by one
  3. (c) Increases by two
  4. (d) Remains the same
Answer & solution

Answer: (d) Remains the same

Topic: Periodic Table - Group Properties
Elements in the same group have the same number of valence electrons.
Example: Group 1 (Li, Na, K, Rb) all have 1 valence electron.
Group 17 (F, Cl, Br, I) all have 7 valence electrons.
Moving down a group → shells increase, but valence electrons remain constant.
Answer: Option 4 → Remains the same
RRB NTPC UG CBT-1 2025-26 – 13 June 2026 Shift 3 · Periodic trends (atomic size, metallic character, electronegativity, ionisation energy)

Q12. Which factors are responsible for the increase in metallic character down a group in the periodic table?

  1. (a) Decreasing ionization energy and increasing atomic size
  2. (b) Increasing ionization energy and decreasing atomic size
  3. (c) Constant ionization energy and decreasing atomic size
  4. (d) Increasing atomic size and constant ionization energy
Answer & solution

Answer: (a) Decreasing ionization energy and increasing atomic size

Metallic Character Down a Group
As we move down a group:
•Atomic size increases(more electron shells added)
•Ionization energy decreases(outer electrons farther from nucleus)
Metallic character = tendency to lose electrons
Larger atoms with lower ionization energy lose electrons more easily
Hence, metallic character increases down the group
Answer: Option 1 → Decreasing ionization energy and increasing atomic size
SSC GD 2026 – 9 May 2026 Shift 1 · Element families (alkali, alkaline earth, halogens, noble gases)

Q13. Which of the following is NOT a rare earth element?
I. Cerium II. Europium

  1. (a) Only I
  2. (b) Only II
  3. (c) Both I and II
  4. (d) Neither I nor II
Answer & solution

Answer: (d) Neither I nor II

Correct Answer: Neither I nor II — Option (d)
Both Cerium (Ce, atomic number 58) and Europium (Eu, atomic number 63) ARE rare earth elements (REEs). Rare earth elements consist of 17 elements — the 15 lanthanides (lanthanum to lutetium, atomic numbers 57–71), plus scandium (21) and yttrium (39). Cerium is the most abundant rare earth element and is used in catalytic converters, glass polishing, and lighting. Europium is used in fluorescent lamps, LED lighting, and as a red phosphor in TV screens. Since both Cerium and Europium are indeed rare earth elements, neither Statement I nor Statement II is correct when claiming them to be 'not a rare earth element'. Hence, 'Neither I nor II' (i.e., neither is a non-rare-earth element — both ARE rare earths) is correct.
Option (a) Only I — Incorrect: Cerium IS a rare earth element (lanthanide), so Statement I (that Cerium is not a rare earth) is wrong; both I and II are rare earth elements.
Option (b) Only II — Incorrect: Europium IS a rare earth element (lanthanide, atomic number 63), so Statement II (that Europium is not a rare earth) is wrong.
Option (c) Both I and II — Incorrect: Both Cerium and Europium are rare earth elements; the question asks which is NOT a rare earth, and the answer is that neither of them is 'not a rare earth' — both ARE rare earth elements.
RRB NTPC UG CBT-1 2025-26 – 8 May 2026 Shift 1 · Element families (alkali, alkaline earth, halogens, noble gases)

Q14. Why do noble gases exist as gases at room temperature, while halogens exist as solids, liquids, or gases down the group?

  1. (a) Weak intermolecular forces in noble gases
  2. (b) Strong chemical bonds in noble gases
  3. (c) Larger atomic size of noble gases
  4. (d) High reactivity of noble gases
Answer & solution

Answer: (a) Weak intermolecular forces in noble gases

Noble Gases vs Halogens - Physical State
Noble Gases (He, Ne, Ar, Kr, Xe, Rn):
Monoatomic molecules with complete octet
Onlyweak Van der Waals forcesbetween atoms
Very low boiling points → exist as gases
Halogens (F₂, Cl₂, Br₂, I₂):
Diatomic molecules (X₂)
Stronger intermolecular forces down the group
F₂, Cl₂ = gases; Br₂ = liquid; I₂ = solid
Noble gases have weakest intermolecular forces
Hence remain gaseous at room temperature
Answer: Option 1 → Weak intermolecular forces in noble gases
RRB NTPC GL CBT-1 2025-26 – 22 March 2026 Shift 3 · Element families (alkali, alkaline earth, halogens, noble gases)

Q15. Which of the following elements is a gas at room temperature and belongs to Group 17 of the periodic table?

  1. (a) Iodine
  2. (b) Fluorine
  3. (c) Astatine
  4. (d) Bromine
Answer & solution

Answer: (b) Fluorine

Topic: Halogens (Group 17)
Group 17 elements:F, Cl, Br, I, At
Physical states at room temperature:
Fluorine (F₂) → Gas
Chlorine (Cl₂) → Gas
Bromine (Br₂) → Liquid
Iodine (I₂) → Solid
Astatine (At) → Solid (radioactive)
Among options, onlyFluorine is gas.
Answer: Option 2 → Fluorine
RRB NTPC GL CBT-1 2025-26 – 19 March 2026 Shift 1 · Element families (alkali, alkaline earth, halogens, noble gases)

Q16. Which of the following gasses is NOT classified as a noble gas?

  1. (a) Argon
  2. (b) Oxygen
  3. (c) Neon
  4. (d) Helium
Answer & solution

Answer: (b) Oxygen

Noble Gases:Group 18 elements in periodic table
Complete outer electron shell → chemically inert
Noble gases:Helium (He), Neon (Ne), Argon ( Ar ), Krypton (Kr), Xenon (Xe), Radon (Rn)
Oxygen (O₂):Group 16 element, highly reactive
Forms compounds easily → NOT a noble gas
Answer: Option 2 → Oxygen
RRB Technician Grade III 2025-26 – 9 March 2026 Shift 1 · Element facts (names, symbols, atomic numbers)

Q17. Which of the following pairs of element names and symbols is correctly matched?

  1. (a) Mercury – Me
  2. (b) Tin – Sn
  3. (c) Silver – S
  4. (d) Lead – Ld
Answer & solution

Answer: (b) Tin – Sn

Correct option is 2: Tin – Sn.
Symbol 'Sn' comes from the Latin name 'Stannum' for tin.
Mercury's symbol is 'Hg', not 'Me'.
Silver's symbol is 'Ag', not 'S'.
Lead's symbol is 'Pb', not 'Ld'.
Therefore, only Tin – Sn is correctly matched.
RRB Technician Grade III 2025-26 – 6 March 2026 Shift 2 · Periodic trends (atomic size, metallic character, electronegativity, ionisation energy)

Q18. Consider the following statements regarding the size of an atom.
Statement 1: The size of an atom is approximately in the range of 0.1 nm to 0.5 nm.
Statement 2: Atomic size increases as we move from left to right in a period of the periodic table.
Statement 3: The radius of a hydrogen atom is about 10⁻¹⁰ meters.
Which of the above statements is/are correct?

  1. (a) Only 1 and 2
  2. (b) Only 1, 2 and 3
  3. (c) Only 2 and 3
  4. (d) Only 1 and 3
Answer & solution

Answer: (d) Only 1 and 3

Statement 1 is correct: Atomic size generally lies between 0.1 nm and 0.5 nm.
Statement 2 is incorrect: Atomic size decreases from left to right in a period due to increasing nuclear charge pulling electrons closer.
Statement 3 is correct: The radius of a hydrogen atom is about 10⁻¹⁰ meters, which is equivalent to 0.1 nm.
Therefore, only statements 1 and 3 are correct.
Final answer: Option 4
RRB Technician Grade III 2025-26 – 6 March 2026 Shift 1 · Element facts (names, symbols, atomic numbers)

Q19. The symbol ‘B’ represents which element?

  1. (a) Beryllium
  2. (b) Boron
  3. (c) Bromine
  4. (d) Barium
Answer & solution

Answer: (b) Boron

The symbol 'B' is the chemical symbol for Boron.
Other options have different symbols:
Beryllium − Be
Bromine − Br
Barium − Ba
Therefore, 'B' represents Boron.
Final answer: Option 2
SSC MTS 2025 – 20 February 2026 Shift 2 · Element families (alkali, alkaline earth, halogens, noble gases)

Q20. Which of the following is an example of alkali metal?

  1. (a) Manganese
  2. (b) Silver
  3. (c) Gold
  4. (d) Potassium
Answer & solution

Answer: (d) Potassium

Correct Answer: Potassium (Option 4)
Alkali metals are the elements of Group 1 (IA) of the periodic table: Lithium (Li), Sodium (Na), Potassium (K), Rubidium (Rb), Caesium (Cs), and Francium (Fr). Potassium (symbol K) is a classic alkali metal — it is highly reactive, soft, and has one valence electron.
Why other options are wrong:
Option 1 – Manganese (Mn) is a transition metal (Group 7), not an alkali metal.
Option 2 – Silver (Ag) is a transition/noble metal (Group 11), not an alkali metal.
Option 3 – Gold (Au) is also a transition/noble metal (Group 11), not an alkali metal.
RRB JE CBT-1 2025-26 – 20 February 2026 Shift 3 · Element families (alkali, alkaline earth, halogens, noble gases)

Q21. Which element exists as a monoatomic molecule?

  1. (a) Argon
  2. (b) Chlorine
  3. (c) Nitrogen
  4. (d) Oxygen
Answer & solution

Answer: (a) Argon

Correct option: 1
Argon is a noble gas and exists as a monoatomic molecule.
Other elements like chlorine, nitrogen, and oxygen exist as diatomic molecules (Cl2, N2, O2 respectively).
Monoatomic molecules mean single atoms exist independently, which is characteristic of noble gases.
Hence, argon exists as a monoatomic molecule.
SSC MTS 2025 – 13 February 2026 Shift 1 · Mendeleev's periodic table

Q22. Which element was predicted by Dmitri Mendeleev as Eka-Silicon?

  1. (a) Germanium
  2. (b) Gallium
  3. (c) Aluminum
  4. (d) Silicon
Answer & solution

Answer: (a) Germanium

Correct Answer: Option 1 – Germanium
Dmitri Mendeleev, in his periodic table (1869), predicted the existence of several undiscovered elements and named them 'Eka' (meaning 'one beyond' in Sanskrit) + the element above them. Eka-Silicon was predicted to be an element with properties similar to Silicon, positioned below Silicon in the periodic table. In 1886, Clemens Winkler discovered Germanium, which matched all of Mendeleev's predictions for Eka-Silicon — confirming the predictive power of the Periodic Table.
Why other options are wrong:
Option 2 (Gallium): Gallium corresponds to Mendeleev's 'Eka- Aluminium ', not Eka-Silicon.
Option 3 (Aluminum): Aluminum already existed; it is not Eka-Silicon.
Option 4 (Silicon): Silicon itself was already known; Eka-Silicon referred to the undiscovered element below it.
SSC MTS 2025 – 9 February 2026 Shift 1 · Mendeleev's periodic table

Q23. Dmitri Mendeleev was unable to assign the correct position to which element?

  1. (a) Helium
  2. (b) Hydrogen
  3. (c) Oxygen
  4. (d) Chlorine
Answer & solution

Answer: (b) Hydrogen

Correct Answer: 2 (Hydrogen)
Mendeleev faced difficulty in correctly placing Hydrogen in his Periodic Table. Hydrogen shows dual behaviour - it resembles alkali metals (Group IA) in some properties (e.g., it forms H+ ions, combines with non-metals) but also resembles halogens (Group VIIA) in other properties (e.g., it is diatomic, forms hydrides like HCl similar to halides). Due to this dual nature, Mendeleev could not assign hydrogen a definitive correct position.
Option 1 (Helium) is incorrect - Helium was discovered after Mendeleev's table but was correctly placed in the noble gas group.
Option 3 (Oxygen) is incorrect - Oxygen was correctly placed.
Option 4 (Chlorine) is incorrect - the candidate chose this wrong option; Chlorine was correctly placed in Group VIIA.
SSC MTS 2025 – 6 February 2026 Shift 1 · Mendeleev's periodic table

Q24. In Mendeleev's Periodic Table, elements were arranged considering _____.

  1. (a) similarity of chemical properties
  2. (b) similarity of colour
  3. (c) similarity of melting point
  4. (d) alphabetical order
Answer & solution

Answer: (a) similarity of chemical properties

Correct Answer: 1 (similarity of chemical properties)
Mendeleev arranged elements in his Periodic Table (1869) based on increasing atomic mass and the similarity of chemical properties. Elements with similar chemical properties were placed in the same vertical column (group). His periodic law stated that the properties of elements are a periodic function of their atomic masses.
Option 2 (similarity of colour ) is incorrect - colour is a physical property and was not the basis for Mendeleev's arrangement.
Option 3 (similarity of melting point) is incorrect - melting point was not the basis for arrangement.
Option 4 (alphabetical order) is incorrect - elements are not arranged alphabetically in the periodic table.
RRB NTPC UG CBT-1 2024-25 – 9 September 2025 Shift 1 · Element facts (names, symbols, atomic numbers)

Q25. The element with atomic number 21 is ______.

  1. (a) Calcium
  2. (b) Scandium
  3. (c) Titanium
  4. (d) Zinc
Answer & solution

Answer: (b) Scandium

RRB NTPC UG CBT-1 2024-25 – 8 September 2025 Shift 3 · Modern periodic law and table (Moseley)

Q26. In accordance with the Modern Periodic Law, the characteristics of elements are periodic functions of their:

  1. (a) atomic number
  2. (b) atomic mass
  3. (c) atomic weight
  4. (d) isotopic mass
Answer & solution

Answer: (a) atomic number

RRB NTPC UG CBT-1 2024-25 – 3 September 2025 Shift 2 · Groups and periods - position of elements

Q27. Transition elements are generally found in which block of the periodic table?

  1. (a) s-block
  2. (b) p-block
  3. (c) d-block
  4. (d) f-block
Answer & solution

Answer: (c) d-block

RRB NTPC UG CBT-1 2024-25 – 1 September 2025 Shift 2 · Groups and periods - position of elements

Q28. Which of the following elements belongs to the s-block of the periodic table?

  1. (a) Iron
  2. (b) Uranium
  3. (c) Calcium
  4. (d) Chlorine
Answer & solution

Answer: (c) Calcium

RRB NTPC UG CBT-1 2024-25 – 1 September 2025 Shift 2 · Periodic trends (atomic size, metallic character, electronegativity, ionisation energy)

Q29. Which of the following elements has the largest atomic radius?

  1. (a) Rb
  2. (b) Li
  3. (c) K
  4. (d) Na
Answer & solution

Answer: (a) Rb

RRB NTPC UG CBT-1 2024-25 – 29 August 2025 Shift 2 · Periodic trends (atomic size, metallic character, electronegativity, ionisation energy)

Q30. Which of the following properties generally increases across a period (left to right) in the periodic table?

  1. (a) Atomic radius
  2. (b) Metallic character
  3. (c) Reduction
  4. (d) Ionisation enthalpy
Answer & solution

Answer: (d) Ionisation enthalpy

RRB NTPC UG CBT-1 2024-25 – 18 August 2025 Shift 3 · Element families (alkali, alkaline earth, halogens, noble gases)

Q31. Which of the following elements is classified as a lanthanoid group element?

  1. (a) Yttrium
  2. (b) Actinium
  3. (c) Scandium
  4. (d) Cerium
Answer & solution

Answer: (d) Cerium

RRB NTPC UG CBT-1 2024-25 – 14 August 2025 Shift 1 · Dobereiner's triads

Q32. What name did Dobereiner give to his groups of three similar elements?

  1. (a) Triangles
  2. (b) Triads
  3. (c) Triplets
  4. (d) Triodes
Answer & solution

Answer: (b) Triads

RRB NTPC UG CBT-1 2024-25 – 14 August 2025 Shift 2 · Mendeleev's periodic table

Q33. In 1869, who is credited with publishing the first widely recognized version of the periodic table?

  1. (a) John Alexander Newlands
  2. (b) Dmitri Mendeleev
  3. (c) Johann Dobereiner
  4. (d) Lothar Meyer
Answer & solution

Answer: (b) Dmitri Mendeleev

RRB NTPC UG CBT-1 2024-25 – 11 August 2025 Shift 3 · Groups and periods - position of elements

Q34. Which of the following elements is found in the p-block?

  1. (a) Barium
  2. (b) Nitrogen
  3. (c) Sodium
  4. (d) Chromium
Answer & solution

Answer: (b) Nitrogen

RRB NTPC UG CBT-1 2024-25 – 7 August 2025 Shift 1 · Element families (alkali, alkaline earth, halogens, noble gases)

Q35. Which of the following elements is classified as an actinoid group element?

  1. (a) Ytterbium
  2. (b) Cerium
  3. (c) Thorium
  4. (d) Lanthanum
Answer & solution

Answer: (c) Thorium

RRB NTPC UG CBT-1 2024-25 – 7 August 2025 Shift 3 · Groups and periods - position of elements

Q36. In which of the following groups does hydrogen belong?

  1. (a) Group 2
  2. (b) Group 17
  3. (c) Group 1
  4. (d) Group 18
Answer & solution

Answer: (c) Group 1

RRB NTPC GL CBT-1 2024-25 – 23 June 2025 Shift 3 · Mendeleev's periodic table

Q37. Why did Mendeleev leave gaps in his periodic table?

  1. (a) To make the table look symmetrical
  2. (b) To avoid repetition of elements
  3. (c) For undiscovered elements
  4. (d) To include isotopes
Answer & solution

Answer: (c) For undiscovered elements

RRB NTPC GL CBT-1 2024-25 – 21 June 2025 Shift 1 · Groups and periods - position of elements

Q38. What does the horizontal row in the periodic table represent?

  1. (a) Periods
  2. (b) Groups
  3. (c) Columns
  4. (d) Blocks
Answer & solution

Answer: (a) Periods

RRB NTPC GL CBT-1 2024-25 – 21 June 2025 Shift 1 · Groups and periods - position of elements

Q39. Which of the following statements is correct with reference to the representative elements?

  1. (a) They only include p-block elements.
  2. (b) They are also called Transuranium elements.
  3. (c) They consist of both s- and p-block elements.
  4. (d) They contain only metals.
Answer & solution

Answer: (c) They consist of both s- and p-block elements.

RRB NTPC GL CBT-1 2024-25 – 20 June 2025 Shift 2 · Modern periodic law and table (Moseley)

Q40. Which of the following statements is NOT correct with reference to the modern periodic table?

  1. (a) The first period contains 8 elements.
  2. (b) Lanthanoids and actinoids are placed in separate panels at the bottom.
  3. (c) Groups are the vertical columns, and periods are horizontal rows.
  4. (d) The second and third periods each contain 8 elements.
Answer & solution

Answer: (a) The first period contains 8 elements.

RRB NTPC GL CBT-1 2024-25 – 19 June 2025 Shift 2 · Groups and periods - position of elements

Q41. Which of the following statements is NOT correct with reference to the main group elements?

  1. (a) They include both s-block and p-block elements.
  2. (b) They are also called representative elements.
  3. (c) Their reactivity does not follow any periodic trend.
  4. (d) Their valence shell configurations help predict chemical behaviour.
Answer & solution

Answer: (c) Their reactivity does not follow any periodic trend.

RRB NTPC GL CBT-1 2024-25 – 18 June 2025 Shift 3 · Periodic trends (atomic size, metallic character, electronegativity, ionisation energy)

Q42. Which of the following statements is NOT correct with reference to the periodic trend of metallic character?

  1. (a) Metallic character increases across a period from left to right.
  2. (b) Metallic character increases down a group.
  3. (c) The change from metallic to non-metallic is gradual.
  4. (d) Metallic character decreases across a period from left to right.
Answer & solution

Answer: (a) Metallic character increases across a period from left to right.

RRB NTPC GL CBT-1 2024-25 – 16 June 2025 Shift 2 · Mendeleev's periodic table

Q43. In which year did Mendeleev publish the periodic table?

  1. (a) 1903
  2. (b) 1869
  3. (c) 1894
  4. (d) 1948
Answer & solution

Answer: (b) 1869

RRB NTPC GL CBT-1 2024-25 – 14 June 2025 Shift 2 · Groups and periods - position of elements

Q44. Which of the following statements is NOT correct with reference to the distribution of elements in the periodic table?

  1. (a) Metals are located on the left side.
  2. (b) There is a zig-zag line separating metals and non-metals.
  3. (c) Non-metals are on the top right corner.
  4. (d) Metalloids are scattered randomly throughout the table.
Answer & solution

Answer: (d) Metalloids are scattered randomly throughout the table.

RRB NTPC GL CBT-1 2024-25 – 14 June 2025 Shift 1 · Groups and periods - position of elements

Q45. What is another name for representative elements?

  1. (a) Inner-Transition elements
  2. (b) Transuranium elements
  3. (c) Transition elements
  4. (d) Main group elements
Answer & solution

Answer: (d) Main group elements

RRB NTPC GL CBT-1 2024-25 – 12 June 2025 Shift 1 · Mendeleev's periodic table

Q46. Which group did iodine belong to in Mendeleev’s table?

  1. (a) Group VIII
  2. (b) Group V
  3. (c) Group VII
  4. (d) Group VI
Answer & solution

Answer: (c) Group VII

RRB NTPC GL CBT-1 2024-25 – 11 June 2025 Shift 2 · Mendeleev's periodic table

Q47. What was the unknown element under aluminium called?

  1. (a) Proto-Aluminium
  2. (b) Neo-Aluminium
  3. (c) Eka-Aluminium
  4. (d) Meta-Aluminium
Answer & solution

Answer: (c) Eka-Aluminium

RRB NTPC GL CBT-1 2024-25 – 10 June 2025 Shift 2 · Element facts (names, symbols, atomic numbers)

Q48. Which statement is correct with reference to Neptunium?

  1. (a) It is stable element.
  2. (b) It is non-reactive element.
  3. (c) It was known during Mendeleev’s time.
  4. (d) It is a naturally occurring element found in pitchblende.
Answer & solution

Answer: (d) It is a naturally occurring element found in pitchblende.

RRB NTPC GL CBT-1 2024-25 – 10 June 2025 Shift 3 · Modern periodic law and table (Moseley)

Q49. How many naturally occurring elements did the periodic law originally reveal analogies among?

  1. (a) 89
  2. (b) 91
  3. (c) 94
  4. (d) 96
Answer & solution

Answer: (c) 94

RRB NTPC GL CBT-1 2024-25 – 9 June 2025 Shift 1 · Element facts (names, symbols, atomic numbers)

Q50. Which statement is correct with reference to artificially produced elements?

  1. (a) They are long-lived.
  2. (b) They are short-lived.
  3. (c) They are found in all groups of the table.
  4. (d) They are stable like natural elements.
Answer & solution

Answer: (b) They are short-lived.

RRB NTPC GL CBT-1 2024-25 – 9 June 2025 Shift 2 · Mendeleev's periodic table

Q51. Where did Mendeleev arrange the elements in the periodic table with similar properties?

  1. (a) Horizontal row
  2. (b) Block
  3. (c) Atomic series
  4. (d) Vertical column
Answer & solution

Answer: (d) Vertical column

RRB NTPC GL CBT-1 2024-25 – 6 June 2025 Shift 1 · Groups and periods - position of elements

Q52. Which of the following statements is NOT correct with reference to the p-block elements?

  1. (a) Their outermost configuration varies from ns²np¹ to ns²np⁶.
  2. (b) They include non-metals and noble gases.
  3. (c) They belong to Groups 13 to 18.
  4. (d) They are also called transition elements.
Answer & solution

Answer: (d) They are also called transition elements.

RRB NTPC GL CBT-1 2024-25 – 5 June 2025 Shift 2 · Mendeleev's periodic table

Q53. In which order did Mendeleev arrange the elements in his periodic table?

  1. (a) Increasing atomic number
  2. (b) Increasing atomic mass
  3. (c) Decreasing atomic radius
  4. (d) Increasing number of neutrons
Answer & solution

Answer: (b) Increasing atomic mass

RRB Technician Grade III 2024-25 – 30 December 2024 Shift 1 · Element families (alkali, alkaline earth, halogens, noble gases)

Q54. Which of the following elements is monoatomic?

  1. (a) Nitrogen
  2. (b) Hydrogen
  3. (c) Oxygen
  4. (d) Helium
Answer & solution

Answer: (d) Helium

Correct Answer: Option 4 — Helium
The atomicity of an element is the number of atoms present in one molecule of that element. An element whose molecule contains only one atom is called monoatomic.
Helium (He) has the electronic configuration K = 2, i.e. its only shell is completely filled (duplet). Having no tendency to gain, lose or share electrons, a helium atom is already chemically stable and does not bond with a second atom. It therefore exists as a single free atom — He, and is monoatomic. All noble gases (He, Ne, Ar, Kr, Xe, Rn) behave this way, and so do metals such as Na, Fe and Cu when their atomicity is counted.
❌ Why the other options are incorrect
✗ Nitrogen — exists as N₂, in which the two atoms are held by a triple bond; it is diatomic, not monoatomic.
✗ Hydrogen — exists as H₂; a single H atom has only one electron in the K shell and must pair up to complete its duplet, so it is diatomic.
✗ Oxygen — exists as O₂ with a double bond, hence diatomic (its allotrope ozone, O₃, is triatomic).
📌 SSC & Railway Exam Facts
• Monoatomic: all noble gases — He, Ne, Ar, Kr, Xe, Rn — and metals such as Na, Cu, Fe.
• Diatomic: H₂, N₂, O₂, F₂, Cl₂, Br₂, I₂.
• Triatomic: O₃ (ozone); Tetratomic: P₄; Octatomic: S₈.
• Helium is the second most abundant element in the universe and is used in weather balloons and in divers' breathing mixtures (with oxygen).
• Noble gases are inert because their outermost shell is complete — 2 electrons in He, 8 in the rest.
RRB Technician Grade III 2024-25 – 28 December 2024 Shift 1 · Periodic trends (atomic size, metallic character, electronegativity, ionisation energy)

Q55. Select the most appropriate hydrogen atom radius from the given options.

  1. (a) 10⁻¹⁰ m
  2. (b) 10⁻⁸ m
  3. (c) 10⁻⁶ m
  4. (d) 10⁻¹² m
Answer & solution

Answer: (a) 10⁻¹⁰ m

Correct Answer: Option 1 — 10⁻¹⁰ m
Atoms are extremely small. The radius of a hydrogen atom — the smallest atom of all — is about 0.53 Å, that is 5.3 × 10⁻¹¹ m, which to the nearest power of ten is 10⁻¹⁰ m. This value, 0.53 Å, is the famous Bohr radius (a₀), the radius of the first orbit (n = 1) in Bohr's model of the hydrogen atom.
Because atomic radii are so small, chemists prefer the unit angstrom: 1 Å = 10⁻¹⁰ m = 10⁻⁸ cm. Atomic radii of ordinary elements lie in the range 0.3 Å to 2.5 Å, so 10⁻¹⁰ m is the correct order of magnitude for any atom, hydrogen included.
Compare this with the nucleus, which is only about 10⁻¹⁵ m across — the atom is roughly 100,000 times larger than its nucleus, which is why Rutherford concluded that an atom is mostly empty space.
❌ Why the other options are incorrect
✗ 10⁻⁸ m — this is 100 times too large; 10⁻⁸ m = 100 Å, a size that belongs to large molecules and small colloidal particles, not to a single atom.
✗ 10⁻⁶ m — this is 1 micrometre (1 μm), about 10,000 times an atom's size; it is the scale of bacteria and fine dust, visible under a microscope.
✗ 10⁻¹² m — this is 1000 times too small; it lies between the size of an atom and that of a nucleus (10⁻¹⁵ m), and no atom is that small.
📌 SSC & Railway Exam Facts
• 1 Å = 10⁻¹⁰ m; atomic radius ≈ 10⁻¹⁰ m, nuclear radius ≈ 10⁻¹⁵ m (1 fermi = 10⁻¹⁵ m).
• Bohr radius of hydrogen = 0.53 Å; hydrogen is the smallest and lightest atom.
• Atomic radius decreases across a period (left → right) and increases down a group.
• An atom is about 10⁵ times bigger than its nucleus — the atom is mostly empty space.
• 1 nm = 10⁻⁹ m = 10 Å; colloidal particles are 1–1000 nm.
RRB Technician Grade III 2024-25 – 23 December 2024 Shift 1 · Element facts (names, symbols, atomic numbers)

Q56. The atomic number of phosphorus atom is:

  1. (a) 15
  2. (b) 17
  3. (c) 14
  4. (d) 16
Answer & solution

Answer: (a) 15

Correct Answer: Option 1 — 15
The atomic number (Z) of an element is the number of protons in the nucleus of its atom. Phosphorus (P) has 15 protons, so its atomic number is 15. A neutral phosphorus atom therefore also has 15 electrons, arranged as 2, 8, 5 (K = 2, L = 8, M = 5).
Since its outermost shell holds 5 valence electrons, phosphorus needs 3 more to complete its octet — hence its usual valency of 3, seen in PH₃ (phosphine) and P₂O₃, though it also shows a valency of 5 in P₂O₅. It belongs to Group 15, Period 3 of the modern periodic table and has a mass number of 31 (15 protons + 16 neutrons).
Phosphorus occurs mainly as white/yellow phosphorus (P₄), stored under water because it ignites in air, and as the safer red phosphorus used on matchbox strikers.
❌ Why the other options are incorrect
✗ 17 — this is the atomic number of chlorine (Cl), whose electronic configuration is 2, 8, 7.
✗ 14 — this is the atomic number of silicon (Si), the element standing just before phosphorus in Period 3.
✗ 16 — this is the atomic number of sulphur (S), the element just after phosphorus; 16 is also the number of neutrons in a P-31 atom, which makes it a tempting wrong choice.
📌 SSC & Railway Exam Facts
• Period 3 in order: Na (11), Mg (12), Al (13), Si (14), P (15), S (16), Cl (17), Ar (18).
• Phosphorus: Z = 15, A = 31, configuration 2, 8, 5; Group 15, Period 3; valency 3 (also 5).
• White phosphorus (P₄) is kept under water; red phosphorus is used in safety matches.
• Phosphorus is the P of NPK fertilisers; in the body it builds bones and teeth and forms part of ATP and DNA.
• Atomic number = protons; mass number = protons + neutrons; neutrons in P-31 = 31 − 15 = 16.

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